Banisteriopsis caapi, also known as ayahuasca, caapi or yagé, is a South American liana of the family Malpighiaceae. It is used to prepare ayahuasca, a decoction with a long history of its entheogenic use and its status as a "plant teacher" among the indigenous peoples of the Amazon rainforest. It contains the harmala alkaloids harmine, harmaline, and tetrahydroharmine. These alkaloids of the beta-carboline class act as monoamine oxidase inhibitor (MAOIs). The MAOIs allow the primary psychoactive compound, DMT, which is introduced from the other main ingredient in ayahausca Psychotria viridis, to be orally active. The stems contain 0.11–0.83% beta-carbolines, with harmine and tetrahydroharmine as the major components. Alkaloids are present in all parts of the plant.